Communication using chaotic waveforms

Abstract

Example communication systems and methods are described. In one implementation, a method receives a first chaotic sequence of a first temporal length, and a second chaotic sequence of a second temporal length. The method also receives a data symbol for communication to a destination. Based on the data symbol, the second chaotic sequence is temporally shifted and combined with the first chaotic sequence to generate a composite chaotic sequence. The first chaotic sequence functions as a reference chaotic sequence while the second chaotic sequence functions as a data-carrying auxiliary chaotic sequence.

The invention claimed is: 
     
       1. A method comprising:
 receiving a first chaotic sequence of a first temporal length; 
 receiving a second chaotic sequence of a second temporal length; 
 temporally shifting the second chaotic sequence relative to the first chaotic sequence to obtain a temporally shifted second chaotic sequence, wherein temporally shifting the second chaotic sequence generates residual samples beyond the second temporal length, and wherein the residual samples of the temporally-shifted second chaotic sequence are wrapped around the starting point of the second chaotic sequence; and 
 combining, using one or more processors, the first chaotic sequence and the second chaotic sequence to generate a composite chaotic sequence such that the first chaotic sequence serves as a reference chaotic sequence and the second chaotic sequence serves as an auxiliary chaotic sequence. 
 
     
     
       2. The method of  claim 1 , further comprising transmitting the composite chaotic sequence to a destination. 
     
     
       3. The method of  claim 1 , further comprising combining the reference chaotic sequence with a plurality of data-carrying auxiliary chaotic sequences, wherein each data-carrying auxiliary chaotic sequence has a third temporal length, and wherein each data-carrying auxiliary chaotic sequence is independently temporally shifted relative to the reference chaotic sequence. 
     
     
       4. The method of  claim 3 , wherein each data-carrying auxiliary chaotic sequence is independently shifted in the frequency domain relative to the reference chaotic sequence. 
     
     
       5. The method of  claim 4 , further including applying standard modulation schemes to at least one of the first chaotic sequence, the second chaotic sequence, and the data-carrying auxiliary chaotic sequences, wherein standard modulation schemes include at least one of quadrature amplitude modulation and quadrature phase shift keying. 
     
     
       6. The method of  claim 1 , wherein each point of the reference chaotic sequence and each point of the auxiliary chaotic sequence are added together to generate each point of the composite chaotic sequence. 
     
     
       7. The method of  claim 1 , wherein a power level of the reference chaotic sequence is greater than a power level of the auxiliary chaotic sequence. 
     
     
       8. A method comprising:
 receiving a composite chaotic sequence that includes a combination of a first chaotic sequence and a second chaotic sequence, wherein the first chaotic sequence is a reference chaotic sequence of a first temporal length, wherein the second chaotic sequence is of a second temporal length, wherein an original chaotic sequence is temporally shifted with respect to the first chaotic sequence to obtain the second chaotic sequence, wherein the original chaotic sequence is temporally shifted in a manner that generates residual samples beyond the second temporal length, and wherein the residual samples of the original chaotic sequence are wrapped around the starting point of the second chaotic sequence in the second chaotic sequence; 
 demodulating, using one or more processors, the composite chaotic sequence to extract the reference chaotic sequence; 
 demodulating, using the one or more processors, the composite chaotic sequence to extract the second chaotic sequence; and 
 determining the temporal shift of the second chaotic sequence with respect to the reference chaotic sequence. 
 
     
     
       9. The method of  claim 8 , wherein the composite chaotic sequence includes a plurality of auxiliary chaotic sequences wherein each auxiliary chaotic sequence is independently temporally shifted with respect to the reference chaotic sequence. 
     
     
       10. The method of  claim 9 , wherein each auxiliary chaotic sequence is independently shifted in the frequency domain with respect to the reference chaotic sequence. 
     
     
       11. The method of  claim 10 , further including determining the shifts in the time-domain and frequency-domain associated with each auxiliary chaotic sequence relative to the reference chaotic sequence. 
     
     
       12. The method of  claim 11 , further comprising mapping a shift in the time-domain and frequency-domain to a data symbol. 
     
     
       13. The method of  claim 8 , wherein demodulating the composite chaotic sequence to extract the reference chaotic sequence is performed by a correlation function that uses a copy of the reference chaotic, and wherein the correlation function provides a correlation peak associated with a starting point of the reference chaotic sequence. 
     
     
       14. The method of  claim 13 , wherein demodulating the composite chaotic sequence to extract the second chaotic sequence is performed by a correlation function that uses a copy of the second chaotic sequence at the receiver, and wherein the correlation function provides a correlation peak associated with the starting point of the second chaotic sequence. 
     
     
       15. The method of  claim 14 , wherein a temporal difference between the correlation peak associated with the reference chaotic sequence and the correlation peak associated with the second chaotic sequence is used to extract a data symbol associated with the second chaotic sequence. 
     
     
       16. An apparatus comprising:
 a discrete-time waveform generator configured to generate a discrete-time waveform, wherein the discrete-time waveform generator is also configured to modulate the phase or the frequency of the discrete-time waveform with an external signal; and 
 a discrete-time signal generator distinct from the discrete-time waveform generator, wherein an output of the discrete-time digital signal generator functions as the external signal, wherein the discrete-time signal generator is a binary counter, and wherein the modulated discrete-time waveform is a chaotic waveform.